Q: What is the "Big Idea"?Top of PageA: The "Big Idea" is a result of the model that BK Butler used to inspire him to invent the TubeDriver BLUE circuitry. For more than 25 years, BK Butler designed tube related audio equipment for various applications. After many innovative tube-driven products, including the original 1995 design of the TubeDriver 1500, BK set out to find a way to unlock the secrets of how to meet the criteria specified in the Russell O. Hamm white paper "Tubes vs. Transistors - Is There an Audible Difference?" That paper is the most definitive study ever undertaken to determine what makes up "tube sound" and why it is better.

After BK Butler's critical subjective and in-depth technical analysis of this brilliantly written research paper, the two essential areas defining vacuum tube sound were disclosed:

"The basic cause of the difference in tube and transistor sound is the weighting of harmonic distortion components in the amplifier's overload region."

The now-patented TubeDriver BLUE circuit design accurately fulfills both of these essential requirements for tube sound:

By directly interfacing the mechanical-electrical speaker load with twin-triode vacuum tubes, TubeDriver BLUE produces the response and tonality of 'all tube' power amplifiers.

Utilizing the original pure Edison effect, the TubeDriver BLUE circuit design safely biases the twin-triode tubes to a constant, near plate-saturated or overload condition. The results are greatly expanded dynamics, punch and presence from naturally produced vacuum tube harmonics.

Q: What is the Russell O. Hamm white paper? Why is it important?Top of PageA: It is the most definitive study ever undertaken to determine what makes up "tube sound" and why it is better. It is important for two reasons:

It clearly outlines two specific points that answer two key questions:
a) if tubes sound different than transistors
and more importantly
b) why they sound different and what it takes to produce that "sound".

It inspired BK Butler to develop the TubeDriver BLUE technology that specifically addresses the points outlined in the Russell O. Hamm study and that you enjoy today.

Q: What is "negative feedback"?Top of PageA: It is a design method used to reduce THD in the output signal in which a portion of the signal from a later amplifier stage is "fed back" to an earlier stage (or to the same stage) in such a manner as to subtract from the input signal and is usually measured in dB. Although it is advantageous in reducing distortion to lower levels, it degrades the overall sonic quality of the output. The more negative feedback is applied to the circuit, the more the overall sonic quality is degraded. Part of the sonic virtues of the TubeDriver BLUE amplifiers is that all BK Butler designs employ ZERO negative feedback.

Q: What does "single ended" mean?Top of PageA: An electrical connection where one wire carries the signal and another wire or shield is connected to electrical ground. This is in contrast to a differential connection where the second wire carries an inverted signal.

A single-ended amplifier has only one input, and all voltages are measured in reference to signal common. Single-ended is a misnomer, since the input voltage is measured relative to signal ground. Vout is equal to Vin multiplied by the gain of the amplifier. A feature of single-ended amplifiers is that only one measurement point is needed. The following is a diagram for a single-ended amplifier:

Q: What type of speaker connectors do you use?Top of PageA: Dual connection (both positive and negative) Hard Gold Plated 5-way binding posts are used for each channel.

Q: Should I turn off the amplifier after every use? Or can I just leave it on?Top of PageA: The current consumption at idle of Tube Driver BLUE amplifiers is very low, thus the amplifiers run very cool and can be either turned off after each use or left on at all times. Tube wear is a non-issue; unlike typical tube designs, part of Tube Driver BLUE's unique and patented circuit is that the tubes are driven at very low voltages and well within their SOA (Safe Operating Area) and maintaining the amplifier in an "on" state has no affect on tube life. Thus, the choice is up to you.

Q: What brand interconnects/wire do you recommend?Top of PageA: We believe that interconnect (RCA) cables and speaker wire selection have more to do with personal taste than with measurable differences in the various manufacturers products. For that reason, we do not recommend a specific brand of wire but rather suggest that within reason, it has been our experience that you get what you pay for in cables/wire. A good set of shielded or twisted-pair interconnects (RCAs) with quality strain relief will be sufficient. "Directionality" is unimportant. The cable "geometry" (design) is less important than the overall build quality.

Q: What does it mean to "bridge" an amplifier?Top of PageA: To "bridge" an amplifier is to use 2 output channels to drive a single load. The sources of power are one output from either channel of the amplifier. It is commonly used to increase the power output of an amplifier.

Q: Are Tube Driver BLUE home amplifiers bridgeable?Top of PageA: The TDB 2250 is designed to operate in either stereo or bridged mode. It has a Mono/Stereo selector switch on the back panel and a seperate connector specifically for mono/bridged operation.

To operate the TDB 2250 in bridged mode, you connect a single RCA to the Channel 1 RCA jack, set the Stereo/Mono switch to Mono (down) and then connect the speaker wire to the mono binding post connector (the center one). Minimum speaker impedance in Mono mode is 6-8 Ohms.

DO NOT attempt to bridge either the TDB 3150 or the TDB 5150 amplifiers as this creates a short and will cause the amplifier to shut down.

Q: How much power does the TDB2250 amplifier produce in bridged mode?Top of PageA: You can find this on the TDB2250 amplifier specs page.

Q: What is a monoblock amplifier?Top of PageA: A single channel amplifier designed to accept one audio channel (either left or right) and drive one speaker. Monoblock amplifiers operate in pairs, one for each of the left and right channels. Monoblock can also refer to a stereo amplifier operating in bridged (mono) mode. The advantage of operating monoblock amplifiers is multifold:

Since there is only one channel of information fed to the amplifier, it completely eliminates crosstalk between channels

With only one channel to drive, the amplifier's power supply is able to provide greater headroom

In low frequency amplification, it provides better phase coherence and less distortion than stereo operation.

Q: What are the amplifier's dimensions?Top of PageA: You can find this on the amplifiers specs page. Click on the specific model number below...

Q: What type of tube is used in the amplifiers?Top of PageA: TubeDriver BLUE home audio amplifiers use a 6SL7GT twin triode, one for each channel. This tube was specifically chosen for its thermionic output characteristics within the circuit.

Q: Can I "tube roll"?Top of PageA: If the question means "can you change the tubes that come with the amplifier to another type", the answer is yes, and no. Yes, if you are skilled in electronics, you could change the tube. And no, it is not easily performed nor desired:

The tubes are soldered into place for reliability thus you would need to change not only the tube but also the mounting scheme in order to accommodate a different type of tube

The circuit is not designed to accommodate any other tube and no other tube type will perform better.

Q: What is "tube rolling"?Top of PageA: "Tube rolling" is a term used to describe when a person decides to alter the sound of a tube amplifier by changing the output tube to a different type/version on the premise that various tube types "sound" different. The premise is based on the idea that each different tube type has a different electrical characteristic and that by testing various tube types, you will find the "magic one" that will make the amplifier sound the best. Unfortunately, this "idea" stems from experiences people have with "typical" tube amplifiers. Because the TubeDriver BLUE amplifiers employ the patented TubeDriver BLUE circuitry, tube rolling is neither necessary nor desired. The patented TubeDriver BLUE circuitry delivers the "live stage" and "recording studio" sound via the thermionic emissions of the tube rather than the overload characteristics of the tube, like typical tube amplifiers. The 6SL7GT twin-triode tube was specifically selected for it's thermionic/emissive qualities and is an integral component in the natural, transparent, clean sound TubeDrive BLUE amplifiers deliver.

Q: Do the tubes break?Top of PageA: The design of the amplifiers makes the tubes very shock resistant and they have proven extremely reliable over time. The only time you should experience a tube failure is if a tube is directly struck and the glass cracks, releasing the vacuum. A cracked tube voids the warranty.

Q: Do the tubes wear out? How often will I need to change the tubes?Top of PageA: The tubes are driven at less than 5% of their maximum rating and thus are not stressed like in a typical tube amplifier. Under normal use, they should not need replacement.

Q: What is the input sensitivity of the amplifiers?Top of PageA: You can find this on the amplifiers specs page. Click on the specific model number below...

Q: What is "signal to noise (S/N) ratio"?Top of PageA: The ratio of the level of the maximum signal output to the level of the noise floor of a shorted input. The larger the number is, the better. Usually expressed in dB.

Q: What is "damping factor"? Does it matter?Top of PageA: Damping is defined as the ratio of the load impedance to the output impedance of the amplifier.
Click here to read more about damping and what the numbers really mean.

Q: What is the current draw of the amplifiers?Top of PageA: You can find this on the amplifiers specs page. Click on the specific model number below...

Q: Can I use TubeDriver BLUE amplifiers to drive a subwoofer?Top of PageA: Yes. The TDB2250 amplifier is designed to operate in bridged (mono) mode, delivering over 800 watts into an 8 Ohm load, thus can easily drive any typical subwoofer.

Q: What speakers do you recommend?Top of PageA: We believe that speaker selection has more to do with personal taste than with measurable differences in the various manufacturers products. For that reason, we do not recommend a specific brand of speakers but rather suggest that you audition as many different types of speakers within your budget as you can and narrow down your selections according to what YOU specifically enjoy. A good set of quality speakers should be a lifetime investment and you should always buy as much speaker as you can afford.

Q: You don't make a seven channel amplifier. Can I set up a 7.1 system using your amps?Top of PageA: Tube Driver BLUE home amplifiers were specifically designed to accommodate system configurations of every type:

2 Channel System

a) Use one TDB 2250 in stereo
or
b) Use two TDB 2250, each in bridged (mono) mode

5.1 Channel System

a) Use one TDB 5150 for the five channels
or
b) Use one TDB 2250 for the front main speakers and one TDB 3150 for the center/surround speakers

6.1 Channel System

a) Use three TDB 2250, one for the front speakers, one for the rear speakers and one for the front/rear center speakers
or
b) Use two TDB 3150, one for the front main/front center speakers and one for the rear main/rear center speakers

7.1 Channel System

a) Use two TDB 2250, one for each front speaker in bridged (mono) mode and one TDB 5150 for the center, surround and rear speakers
or
b) Use a TDB 2250 for the front speakers and one TDB 5150 for the center, surround and rear speakers

In any system, you can use a TDB 2250 in bridged (mono) mode to drive passive subwoofer(s). In addition to these system suggestions, you can use the two, three and five channel amplifiers in a variety of combinations to create a system that will suit virtually any power combination you choose.

Q: Do the Tube Driver BLUE home amplifiers have a balanced (XLR) input? Why not?Top of PageA:

Q: Can I use long interconnects (RCAs) with the amplifiers?Top of PageA: Yes. Tube Driver BLUE amplifiers have a 47 Kohm input impedance and are easy to electrically drive. You can find more information on the amplifiers specs page. Click on the specific model number below...

Q: Do the amplifiers come in black?Top of PageA: The standard finish is Frosted Platinum as shown but Black finish may be available. Please contact us for availability: [email protected]

Q: Why do the tubes glow blue?Top of PageA: The faint blue glow that is produced around the positive pole in a vacuum tube was first noticed by a William J. Hammer (see Big Idea), a young engineer employed by Thomas A. Edison. He was in charge of testing early light globes. During his observations, he noted this blue glow and a blackening of the wire and the bulb at the negative pole. This unknown phenomenon was first called "Hammer's Phantom Shadow", but when Edison patented the light bulb in 1883, it became known as the "Edison Effect". It is the after-effect of Thermionic emissions, the basis of modern electron tube theory, the foundation for the entire electronics industry and the "driving force" behind BK Butler's patented Thermionic Tube Driver BLUE technology.

The distinctive blue LED illumination that is a part of all Butler Audio designs is a BK Butler trademark commemorating his breakthru electrical concept and is part of the Tube Driver BLUE technology patent.

Q: How can I tell if a fuse is blown?Top of PageA: You can see if a fuse on a specific power module is blown by looking thru the front panel slots. If a glowing red LED is visible thru one of the front panels slots, a fuse is blown on that associated module. Please contact use for assistance.

Q: Why is the red LED visible thru the front panel?Top of PageA: See "How can I tell if a fuse is blown?" above...

Q: What is the remote jack on the back of the amplifier for?Top of PageA: It is used to turn the amplifiers on and off automatically via a cable connected to a pre-amp or receiver remote output. You connect the pre-amp or receiver's remote out via a cable with 3.5mm (1/8") mini jack connectors (we recommend Radio Shack Part# 420-2387) to the amplifiers remote in. Remember to leave the front panel/power switch in the "OFF" position for remote operation.

Q: What is the remote trigger input voltage?Top of PageA: 8 to 13 Volts DC.

Q: What is the warranty?Top of PageA: TubeDriver BLUE home amplifiers are covered for a period of three years from date of purchase, if you return the included warranty registration card. Otherwise, the warranty is 90 days. Please go to our WARRANTY page for more information.

Q: What is "new" about the TubeDriver BLUE amplifiers?Top of PageA: TubeDriver BLUE amplifiers are a revolutionary new design patented by BK Butler. They are the end result of 25 years of experience in designing tube driven products for some of the world's most demanding end-users; professional musicians. They employ 6SL7GT twin-triode tubes directly coupled to the speaker and mated to audiophile-grade bi-polar devices to produce an amplifier that combines all the highly-desired sonic characteristics of the best in tube amplification (punch, dynamics, liquidity, detail) without any of the limitations (heat, wear, low power, rolled-off frequencies) AND have all the advantages of the best solid state amplifiers (power, current delivery, transparency) without any of the limitations (harshness, edginess, even order harmonic distortion).

The ONLY home audio amplifier to provide the best of both worlds... and its here today... ENJOY! - BK Butler

TubeDriver, TubeDriver BLUE, Thermionic, MosValve, Butler Audio, Blue Tube,
blue tube illumination, appearance and method are trademarks of BK Butler.
Use of these trademarks is by permission only and is strictly enforced.